The use of catheters in the medical field is well known. Catheters are of many different designs depending on the task to be accomplished. For example, the rigid hypodermic needle is widely used for venipuncture for the withdrawal of blood samples or the injection of medicants. Repeated use of such rigid catheters within a short period, such as during hospitalization, is highly traumatic and discomforting to the patient. During hospitalization, it is preferable to place a single catheter in the patient and allow the catheter to remain in place for an extended period.
Placement of a rigid catheter within the patient for an extended period is undesirable because movement of the rigid catheter after implantation causes additional trauma to the patient. When a rigid catheter was implanted for an extended period, the portion of the body in which the rigid catheter was implanted was immobilized to minimize the risk of movement of the rigid catheter relative to the lumen to prevent injury. This practice was uncomfortable and prone to undetected injurious movement when the patient slept.
More recently, it has been the practice to insert a pliant catheter into the vein for an extended period for the periodical administering of fluids, transfusions, medication, collecting blood samples, etc. These flexible catheters are of pliable material and substantially reduce the risk of puncturing the lumen wall in the event of movement relative to the lumen. Two commercial techniques have been used to place the distal end of such flexible catheters within the lumen. They generally may be referred to as the "inside-the-needle" and the "outside-the-needle" techniques. In general, both these methods utilize a rigid catheter, such as a hypodermic needle, for initial penetration of the skin and venipuncture. The "inside-the-needle" technique provides for the insertion of the flexible catheter through the hollow hypodermic needle. Once the flexible catheter is in place, the needle is removed. This technique necessarily requires a small flexible catheter and its attendant disadvantages. Such small catheters are difficult to insert because they easily bend or tear and are difficult to manipulate. Therefore, the implantation of these catheters requires careful manipulation of the needle and catheter which necessitates a relatively long time complete the implantation thereby increasing the risk of injury to the patient.
The "outside-the-needle" technique has the advantages that the catheter may be larger with increased capacity. This technique suffers the disadvantage, however, that the catheter must be rigid enough to penetrate the tissue as it advances to the distal end of a needle. Once the semi-rigid catheter is in place, the needle is then withdrawn from inside the catheter. These semi-rigid catheters suffer the disadvantage that they are more likely to cause additional trauma if they move relative to the lumen. However, the semi-rigid "over-the-needle" catheters, represent an improvement over the rigid metal catheter as they eliminate the sharpened point of the needle.
A third technique has been developed which combines the two prior methods to overcome their disadvantages. This combination technique has two variations.
A first variation of the combination technique involves a multistep procedure. First, a needle is inserted into the vein. A spring wire stylet is introduced into the vein through the needle, after which the needle is removed. A semi-rigid catheter tube and dilator is then placed over the spring wire stylet and guided into position in the vein. Once the semi-rigid catheter is positioned in the patient, the wire stylet and dilator are removed thereby allowing a primary device, such as an infusion catheter, to be inserted therethrough. Once the primary device is in place, the semi-rigid catheter is removed from the patient, and from around the primary device. This method suffers from the disadvantage of requiring a relatively long time for completion, which increases the exposure of the patient to associated injuries.
A second variation of the combined technique is disclosed in co-pending application Ser. No. 259,281 assigned to the assignee of the present invention. This application is entitled "Peelable Catheter Introduction Device". This technique eliminates many of the steps of the previously described combined method. This technique calls for the implantation of an introducer catheter by the "over-the-needle" technique. Once the introducer catheter is in place, the needle is withdrawn leaving a semi-rigid introducer catheter implanted in the patient which is less prone to cause injuries because it is semi-rigid and has a fairly blunt distal end; therefore, it is also less likely to puncture the lumen wall if moved during implantation of the infusion catheter. A pliant infusion catheter is then implanted within the patient through the introducer catheter. Once the pliant infusion catheter is properly placed within the lumen, the introducer catheter is removed from the patient and from around the infusion catheter. In order to facilitate removal of the introducer catheter, the tubes have been mechanically scored to provide weakened lines along which the catheter tube could be ruptured and then peeled apart. This technique permits a larger diameter pliant infusion catheter to be implanted within the patient than is normally possible by the previous "inside-the-needle" technique. Also, this dual technique is less likely to cause additional trauma to the patient, because the semi-rigid inducer catheter with a fairly blunt end is less likely to puncture the lumen wall if moved during implantation of the infusion catheter. In addition, the larger diameter infusion catheter is more easily manipulated and is less likely to fold, bend or tear during implantation. Thus, it may be more quickly implanted thereby reducing the period of time the patient is exposed to the risks associated with implantation.
Introducer catheters of the semi-rigid design have also been utilized to insert diagnostic and therapeutic devices, e.g., pacemaker leads. In some applications, the device inserted through the introducer catheter is to be implanted within the patient for a period of time, and in these applications, a peelable introducer catheter is desirable. As used herein, "primary device" will refer to the device inserted through the introducer catheter whether it is an infusion catheter, a diagnostic or therapeutic device.
The introducer catheters previously used in a dual technique are free to rotate about the stylet or needle presenting a possible source of abrasion to the tissue during implantation. Previous peelable introducer catheters were also rather difficult to remove from about the infusion catheter once it was implanted because the mechanical scoring of the catheter tube could not be consistently reproduced. Thus, a need has arisen to provide an introducer catheter which does not rotate about the needle during the implantation and from which the needle may easily be removed and which is easily removed from the infusion catheter when desired, but is not subject to premature rupture during its implantation or the subsequent implantation of the infusion catheter.